: The current project has four specific aims designed to elucidate the molecular basis for posttranscriptional regulation of tPA and PAI: 1) isolation and cloning of proteins that bind to the cyclic nucleotide responsive region of the PAI-1 mRNA; 2) analysis of the role of the mRNA binding proteins in the cyclic nucleotide regulation of PAI-1 mRNA degradation, both in intact cells and in a cell free in vitro mRNA decay system; 3) analysis of cyclic nucleotide regulation of the amount, subcellular localization, and posttranslational modification of the PAI-1 mRNA binding proteins; and 4) identification of proteins with which the mRNA binding proteins interact and analysis of their role in cyclic nucleotide regulation of PAI-1 mRNA degradation.